Resisting pressure deep down

Illustration : Thierry Cap de Coume

The great depths of the sea are a tremendous challenge for manufacturers of subsea flexible pipes for transporting oil to production platforms. “Since the pipes go down as far as 3,000 metres, they need to be sufficiently crush resistant to withstand pressures of up to 300 bars,” says Jeroen Remery, technology coordinator at Technip’s subsea division. Technip, with its workforce of 23,000 employees and revenues of 7.9 billion dollars in 2007 (6.3 billion euros), operates in 3 business segments: onshore, offshore and subsea facilities. It owns a fleet of 19 vessels, three of which are currently under construction, and works with all the major oil companies, including the French group Total and the Brazilian oil company Petrobras in deepwater and ultra-deepwater fields off the shores of Brazil and Angola. Technip produces umbilicals (tubes containing pipes, electrical cables and optical fibres for facility monitoring purposes) and riser systems (rigid or flexible pipes used to transfer fluids from the seabed to production sites) for which the company develops its own advanced simulation tools, such as corrosion-measuring devices placed in the lower part of risers, to improve risk assessment.
In addition to assessment and simulation tools, Technip is focusing heavily on the development of new flexible pipes that can be used at depths exceeding 600m.
Research is well advanced and in 2009/2010 the group will be testing the first carbon flexible pipe for deepwater offshore applications at its Le Trait manufacturing plant in Normandy. The pipe is composed of a composite armour with unidirectional carbon fibres to avoid any risk of its bursting under pressure. In fact, the pipe’s carbon armour provides an improvement on the properties obtained until now with steel offering mechanical resistance of 1,400 megapascals (MPa). And since the pipe has already passed fatigue tests conducted by the French institute of oil, its deep-water future looks to be well on track. The new pipe provides a number of important benefits. Firstly, it halves the total pipe weight; a significant saving when one considers that a metre of pipe generally weighs 400kg. Lighter pipes will also reduce logistical costs since the sea carriage of rigid pipes requires the deployment of expensive specialist vessels. Another benefit is that it will be easier to maintain the pipes on platforms since suspended weight will be between 350 and 400 tonnes for a riser of more than 2,500 m. This will also be the case if the pipe is supported by a buoy, the size of which can be significantly reduced. Finally, in the event of a hurricane, the pipe merely needs to be disconnected from the production platform.

300 million dollars in contracts
In January 2008, Techip secured two major contracts with Petrobras America, subsidiary of Petrobras, with a total value of over 300 million dollars (218 million euros). They consist of developing the gas fields of Cascade and Chinook, located in the Walker Zone Ridge of the Gulf of Mexico, at water depths of respectively 2,500 and 2,700 metres. These contracts include the engineering, equipment supplies, construction and installation of pipelines, notably flexible pipes resistant to deep- sea conditions. Operations should commence in the third quarterly of 2009.